The present invention relates to the construction industry, and more particularly to the formation of a grate-covered trench including an assembly for forming the trench and a novel frame for the assembly.
The use of concrete-lined grate or solid covered trench hereafter called a grate is well known in road, parking lot, and other constructions. The typical trench construction includes a pair of spaced frames, each having a grate supporting surface upon which a metal grate rests. A major problem exists, however, in that in construction, the grate supporting surfaces of the frames must be on a common lateral plane so as to prevent rocking of the grate when a car or other heavy object passes over the trench.
The most common current method of forming a grate-covered trench recognized the need for positioning the frames to provide a properly set grate. A floor slab of the trench is prepared and cured, and a box-like form is placed inside. The form typically has a pair of parallel plywood sidewalls, each corresponding to a trench wall, extending vertically from the floor to the final grade elevation. A number of spreaders, typically consisting of wooden joists, are fastened atop the sidewalls for providing a stop for a frame and seat form. Also, inner bracing is used, consisting of wooden studs attached to the upper edge of a first sidewall at one end and to the lower edge of the second sidewall on the other. A criss-crossed pattern of bracing is achieved by altering the sidewall upper edge upon which the stud is attached. The frame typically consists of an elongate bar having an L-shape when viewed cross-sectionally.
A horizontal grate-supporting surface is provided, upon which an edge of the bottom of the grate rests, and a vertical back surface is provided for contacting the side edges of the grate. The seat form has dimensions identical to the frame, the back surface height and grate supporting surface width of the frame corresponding to the height and width of the seat form. A seat form is attached to the upper edge of the outside surface of each sidewall, and the frame is attached so that the back surface and grate supporting surface contact the seat form, thereby assuring that the frame is at the desired elevation and level. An inner joist is typically placed along the upper edge of the inner surface o each sidewall opposite the seat forms. The frame is typically attached to the seat form with nails or other fasteners.
To hold the frame at the required plane, a hole is provided in the sidewall at a point below the frame, and a 9 gauge wire is placed through the hole and brought over the top of the frame sidewall and inner joist. The two ends of the wire are then intertwined, thereby tightening the frame into position. Adjusting the tension on the wire allows the repositioning of the frame as required. A series of such wire-operated frame positioning means are required along the length of the frame. Only after the entire frame is properly positioned can concrete be poured outside the sidewalls, thereby forming the trench and holding the frame in final place.
It can be seen that this procedure is complicated and involves many steps requiring great attention to detail. Because the frame-positioning means must be constantly adjusted, the construction of trenches using this method is time consuming and, therefore, expensive. Skilled personnel are required to properly position the frames or the grate will not sit properly and the procedure must be repeated from start. Additionally, the need to be able to repeatedly maneuver the frame dictates that the frame be kept to a relatively short length (i.e., approximately two or three feet). Otherwise the frame would be too heavy and could not be moved by manipulation of the wire. This results in a large number of joints along the length of the trench between individual frame sections, thereby resulting in less than optimal stability.
Therefore, there exists a need for an improved method for producing a grate-covered trench.
There also exists a need for such a method of installation which is simple, relatively quick, and which does not require skilled labor.
There exists a further need for such a method which will allow the use of frames of relatively long length, thereby reducing the number of joints along the trench.
There exists a still further need for an improved frame which can be used in the above-mentioned methods.